This invention relates to a front wheel transaxle for a part time on-demand four-wheel drive vehicle and, more particularly, to a dual differential viscous clutch assembly for such a vehicle transaxle.
Constant four-wheel drive vehicle systems having a front wheel transaxle are known in the art. An example of one such system is disclosed in U.S. Pat. No. 4,417,642 issued to Suzuki et al. on Nov. 29, 1983. The Suzuki patent describes a four-wheel drive transaxle incorporating a front to rear interaxle bevel gear differential and a planetary gear differential with a clutch lockout mechanism. The U.S. Pat. No. 3,400,777 issued to C. Hill on Sept. 10, 1968 relates to a three differential four-wheel drive system with a lockout clutch designed for a rear engine drive vehicle. The U.S. Pat. No. 4,476,953 issued to Hiraiwa on Oct. 16, 1984 for a Four-Wheel Vehicle Drive System discloses a transaxle mechanism with two connected bevel gear differentials. The Hiraiwa system requires an intermediate gear mechanism and jack shaft for transmitting driving power to the rear-wheel driveline.